c# - Dynamic lambda expression (OrderBy) and nullable property type -

i'm trying dynamically create expression sort data database through entity framework. encountered 1 problem , cannot overcome it. maybe let me explain i'm trying do. goal create expression this:

x => x.property 

where "property" name of property i'd specify dynamically.

now, let's go class, represents table in database (i simplified make things more clear):

public class mymodelclass {     public long mylongproperty { get; set; }     public decimal? mynullabledecimalproperty { get; set; } // important: it's nullable } 

it code, i'm trying create expression described earlier:

// db entityframework context iqueryable<mymodelclass> list = db.mymodels.select(x => x);  // x => var argument = expression.parameter(list.elementtype, "x");  // x.mynullabledecimalproperty var propertytoorder = expression.property(argument, "mynullabledecimalproperty");  // x => x.mynullabledecimalproperty var finalexpression = expression.call(     typeof (queryable),     "orderby",     new[] { list.elementtype, typeof(icomparable) },     list.expression,     expression.lambda<func<mymodelclass, icomparable>>(propertytoorder, argument));  list = list.provider.createquery<mymodelclass>(finalexpression); 

problem occurs @ 4th statement (var finalexpression = expression.call(...)). exception:

expression of type „system.nullable`1[system.decimal]” cannot used return type „system.icomparable”.

as far understand problem me using "icomparable" type "mynullabledecimalproperty" nullable , nullable doesn't user icomparable interface. exception isn't thrown when i'm ordering "mylongproperty" or when replace "icomparable".

so questions:

1. what type should use make work nullable properties?

2. is possible use 1 type , work properties whether nullable or non-nullable.

notice: know can use ex. dynamic linq library, i'm not interested in solution - i'd learn how overcome without using 3rd party libraries.

there's no reason use icomparable. indeed, many types comparable not implement icomparable. use runtime type of whatever you're passing:

var finalexpression = expression.call(     typeof (queryable),     "orderby",     new[] { list.elementtype, propertytoorder.type },     list.expression,     expression.lambda(propertytoorder, new [] { argument }));